Without limiting the scope of the invention, its background is described in connection with modifying VoIP networks for communicating voice data over a data network.
The transmission of analog voice over the Public Switch Telephone Network (PSTN) is slowly being supplemented by other technologies, such as VoIP. The immediate goal for VoIP service providers is to reproduce existing PSTN capabilities at a significantly lower “total cost of operation” and to offer technically competitive alternatives to the PSTN. It is the combination of VoIP with point of service applications that shows the greatest promise for the long term. VoIP provides a competitive threat to the providers of traditional telephone services that, at the very least, will stimulate improvements in cost and function throughout the industry.
Essentially, VoIP may be applied to almost any voice application including simple inter-office intercom to complex multi-point teleconferencing and shared screen environments. The quality of voice reproduction may also be tailored according to the application. For example, customer calls utilizing voice recognition may need to be of higher quality than internal paging over an overhead paging system. Hence, VoIP equipment must have the flexibility to cater to a wide range of configurations and environments and an ability to blend traditional telephony standards with VoIP.
Despite initial excitement among consumers for VoIP services, customers are worried over possible degradation in voice quality due to packetization of voice into voice packets. Whether these concerns are based on experience with early Internet telephony applications or whether they are based on understanding the nature of packet networks, voice quality is a crucial parameter in acceptance of VoIP services.
In addition, VoIP services need to be able to connect to traditional circuit switch voice networks. The International Telecommunications Union (ITU) has addressed this goal by defining H.323, a set of standards for packet-based multimedia networks. With H.323, the network is able to connect with other H.323 terminals or more traditional phone services such as PSTN, ISDN, or wireless phones. H.323 describes how multimedia communications occur between terminals, network equipment, and services on Virtual Local Area Network (VLANS) which often do not provide a guaranteed quality of service. Due to the support of personal computer, communication systems manufacturers and operating systems makers, H.323 has experienced rapid growth. H.323 compliance has been promoted and accepted by Internet phone and VoIP manufacturers as the standard for interoperability.
In a traditional network, groups of computers and other devices, such as printers, were configured as a Local Area Network (LAN). Each of these devices is generally referred to as an end node device. Hubs, bridges or switches are used in the same physical segment or segments connecting all end node devices. End node devices can communicate with other end node devices on the same LAN without the need for a router.
Communications with end node devices on other LAN segments requires the use of a router or gateway (collectively “router”). Specifically, each LAN is separated from another LAN by a router. As networks expand, more routers are needed to separate users into LANs and provide connectivity to other LANs. One drawback to this design is that routers add latency, which essentially delays the transmission of data. Another disadvantage of a LAN is that LANs are often setup based on location and geographic constraints. For example, in an office building, all the computers and printers on one floor may be members of one LAN while computers and printers on the second floor may be members of another LAN. However, in actual use, it may be advantageous to connect computers from the first floor with those from the second floor. Thus, it would be more convenient to be able to put all of the end node computers that need to talk to each other on the same LAN.
In an attempt to overcome the physical limitations of LANs, Virtual LANs (VLAN) were developed. For large numbers of VoIP devices, a VLAN is typically used. A VLAN can be viewed as a group of devices on different physical LAN segments which can communicate with each other as if they were all on the same physical LAN segment. VLANs provide a number of benefits over a LANs. Using VLANs, it is possible to group computing devices logically into a single broadcast domain. This allows us to define broadcast traffic for this VLAN to just those devices that need to see it and reduce traffic to the rest of the network. Also, with VLANs connection speeds increase due to the elimination of latency from router connections. An additional benefit is increased security since access from foreign networks, i.e, those that originate from another subnet beyond the router, is not allowed.
In order to implement VLANS, IEEE has propagated Standard 802.1Q which defines the requirements for a VLAN network. Additionally, in order to add a priority to data packets flowing through the network, IEEE has propagated Standard 802.1D to specify a 3-bit priority code, which can be encoded into the Ethernet header of the data packet. The three-bit priority code represents numbers 0 through 7, thus creating 8 choices or 8 different priorities. In a VLAN network implementing IEEE Standards 802.1Q/D, a VLAN having packets of different priorities is enabled.
A disadvantage of the present VoIP devices is that the priority is assigned to a default value of 6, regardless of the type of call being processed. There is currently no way to detect if one call is more important than another call. Thus an important call to an ambulance or fire department must contend with all other calls for network resources.
In summary, the prior art methods of routing emergency calls in a VoIP network do not provide flexibility and efficient use of network resources that is needed for today's networks. A system or method which overcomes these problems would have numerous advantages.